KR20080014657A - Method for forming tapered piston pins - Google Patents

Abstract

A tapered piston pin and a method for manufacturing the same are provided to form a taper in a piston pin without mechanical process, coating or additional molding processes. A method for manufacturing a tapered piston pin includes a step of cutting a metal rod into a substantially cylindrical slug piece, a step of die extruding the slug piece such that a first cavity is formed in the slug piece, a step of die extruding the slug piece such that a second cavity is formed in the slug piece, a step of punching the slug piece such that the slug piece is formed in a hollow cylindrical piece, and a step of die extruding the hollow cylindrical piece so as to form the hollow cylindrical piece with a tapered inner surface at both ends.

Description

Tapered piston pin and manufacturing method therefor {METHOD FOR FORMING TAPERED PISTON PINS}

The present invention relates to a method of forming a piston pin, and more particularly, to a method of forming a piston pin having a tapered inner opening in one or a plurality of operations. The present invention also includes a tapered piston pin made using such a process.

Reciprocating internal combustion engines generally use pistons reciprocating in a cylinder. As shown in FIG. 1, the piston 12 functions as a sliding plug that fits closely within the hole of the cylinder. In practice, the piston is driven alternately in the cylinder. Combustion of a mixture of fuel and air on the piston generates gas pressure from the compressed and ignited combustion gases. This pressure forces the piston downward. At this time, the piston transmits a force for expanding the combustion gas through the piston pin 10 to the connecting rod 14. The piston is attached to the connecting rod and the crankshaft to convert the reciprocating motion into rotational motion.

The piston pin forms an important part of the reciprocating internal combustion engine system. Each piston pin extends through aligned openings in the piston and connecting rod, establishing a pivotal connection between the rod and the piston. Rotating the crankshaft of the engine, one end of each connecting rod pivots around the axis of the crankshaft. The other end of the connecting rod rotates around the pin in the piston, whereby each piston transmits power to the crankshaft through the connecting rod. Each piston pin serves as a pivotal connection between the connecting rod and the piston.

The force imposed on the piston, piston pin and connecting rod by combustion is enormous. Moreover, the piston assembly (piston, piston pin and connecting rod described above) causes a large amount of frictional loss in engine performance. It is a trend in engine design to reduce the reciprocating portion of the piston assembly including the crankshaft. As a result, the performance is improved by having a lighter weight piston pin that reduces the inertia loss, so that the engine efficiency can be improved. Therefore, the weight is lowered for the essential characteristics of the effective piston pin and the piston assembly. In addition, the ideal piston pin has other important properties: wear resistance, stiffness and high strength to withstand extreme forces from the combustion process. In order to reduce the weight of the piston pin, there is one method of reducing the mass at the end of the inner diameter by forming an outwardly inclined interior.

Certain piston pins are formed in the center web near the middle of the pin, as shown in FIG. 3. These piston pins are referred to as central web shaped, two way extruded or two way formed piston pins. Another piston pin reduces the weight even further by forming a web on the end of the pin as shown in FIG. 4. In this method, the web is completely removed for the benefit of further reducing the mass. These pins are commonly referred to as webless, end web, one-way extruded or one-way piston pins. The method of making both piston pins may be designed with tapered holes to reduce weight. Current techniques include machining the inner taper into the pin, or extruding the taper into the center web pin. In addition, some taper may be added to the unidirectional pin by adding the taper therein through additional machining or forming operations. These additional operations may include any combination of annealing, lubrication applications, and ancillary molding operations. These methods are not cost effective and are not optimized for weight reduction. All these methods are very expensive.

As mentioned above, the prior art has various defects related to low efficiency, high cost and lane weight reduction. In one forming sequence of a machine, there is a need for a cost effective manufacturing method for forming a central web or webless tapered piston pin. Moreover, there is a need for an improved and more economical method for forming internal taper on piston pins.

In current reciprocating internal combustion engine systems, there is a need for a method for economically manufacturing a central web or webless tapered piston pin with light weight and high strength. According to the present invention, a method is provided for forming a slanted central web or webless piston pin that has been cold treated in an efficient and cost effective process. The present invention eliminates incidental work performed separately or in combinations such as, for example, machining, coating and incidental molding. In another embodiment of the present invention, the taper of the piston pin is formed at a greater angle and length, further reducing the weight than that of the prior art.

3A-4D show a typical process for making a piston pin. These processes begin with a bar or coil steel. In general, carbon steel wire is used not only to effectively provide the necessary properties for the final product cost, but also for reasons relating to the physical and mechanical properties of carbon steel which are advantageous for forming piston pins. However, other metals may be used depending on the application. The metal wire is straightened. After exiting the annealing machine, the metal coil is cut into separate pieces. These pieces are formed into a substantially cylindrical shape. Next, these pieces are prepared for the extrusion process. Depending on the customer's requirements, tapering of the piston pin may be required. The tapering process will be further described with reference to the drawings.

Referring to FIG. 3, a typical two-way / center web extrusion sequence for the manufacture of a piston pin is shown. Everything about cold treatment is understood only as an example of how to form a piston pin. The object of the invention is used by way of example only, and the invention applies to all methods of tapering a tubular extruded semi-finished product.

Referring to FIG. 4, a one-way / end web extrusion sequence for a method of making a piston pin is shown. Everything about cold treatment is understood only as an example of how to form a piston pin. The object of the invention is used by way of example only, and the invention applies to all methods of tapering a tubular extruded semifinished product.

Referring to FIG. 2A, the present invention shows a molding operation for tapering at both ends of the inside of the piston pin semifinished product from the tubular semifinished product 50. FIG. 2A shows the tapering with an included angle 58 which is shorter than the axially finished taper length of the piston pin or larger than the finished portion 52 which is finished to a predetermined length. The final finished contour is shown by reference 56 only as an example. While everything about the molding technique can be completed in one or a plurality of stations, the present invention focuses on the most cost-effective way to taper the inside of the tubular semi-finished product. However, it is an object of the present invention to include a plurality of all sequences which taper inside a tubular semifinished product.

2B shows an example of forming a piston pin with the finished requirements of the finished product 68 from a pre-taper forming operation. 2B shows the finishing tool 62 on the wall 168 of the pre-tapered blank. While everything about the molding technique can be completed in one or a plurality of stations, the present invention focuses on the most cost-effective way to taper the inside of the tubular semi-finished product.

The above described method of tapering piston pins is one embodiment. The method illustrates one approach for tapering in piston pins without the need for expensive machining, coating or additional forming processes. In actual practice, the discussed configuration can be changed. Moreover, various other improvements and modifications of the present invention can be considered by those skilled in the art, and those improvements and changes will fall within the scope of the present invention as set forth in the claims below.

It may be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. The described embodiments are to be considered in all respects only as examples and not by way of limitation. Thus, the scope of the present invention is not limited to the specific exemplary embodiments described above. All changes or modifications within the meaning and range of equivalents are intended to be included within the present invention.

1 is a front view of a piston system having a piston pin pivotally connected between a connecting rod and a piston,

2a shows a wider angle of engagement in a first tapered forming operation showing the next station punch at the initial contact point, FIG.

FIG. 2B shows a narrower angle of engagement in a second taper forming operation showing the next station punch at the initial contact point, FIG.

3A-3D illustrate an exemplary two-way central web extrusion method of making a tapered piston pin;

4A-4D illustrate an exemplary one-way webless extrusion method of making tapered piston pins.

Explanation of symbols for the main parts of the drawings

10: piston pin 12: piston

14: connecting rod 50: tubular semi-finished product

52: finished request 58: angle of angle

62: finishing tools

Claims (18)

In the method of manufacturing the tapered piston pin, Die-extruding the hollow cylindrical piece at both ends to form the hollow cylindrical piece having a tapered length at both ends of the inner surface of the hollow cylindrical piece. The method of claim 1, Inserting initial punches or punches in one or both ends of the hollow cylindrical piece, wherein the initial punches or punches form a taper at a predetermined acute angle on an inner surface of the cylindrical piece; And Inserting subsequent punches or punches into the end or both ends of the hollow cylindrical piece, the subsequent punches or punches forming a second taper at a second predetermined acute angle on an inner surface of the hollow cylindrical piece; A subsequent punch inserting step; further comprising a tapered piston pin manufacturing method. The method of claim 2, And said second predetermined acute angle of said second taper is less than said first predetermined acute angle of said first taper. The method of claim 2, And said second predetermined acute angle of said second taper is greater than said first predetermined acute angle of said first taper. In the method of manufacturing the tapered piston pin, Cutting the metal rod into a substantially cylindrical slug piece; Die extruding the slug piece to form a first cavity in the slug piece; Die extruding the slug piece to form a second cavity in the slug piece; Drilling the slug piece so as to form the slug piece in the hollow cylindrical piece; And And die extruding the hollow cylindrical piece at both ends to form the hollow cylindrical piece having a tapered length at both ends of the inner surface of the hollow cylindrical piece. The method of claim 5, Inserting a first die punch into an end of the hollow cylindrical piece, wherein the first die punch forms a first taper at a first acute angle on an inner surface of the cylindrical piece; And Inserting a second die punch into the end of the hollow cylindrical piece, the second die punch forming a second taper at a second predetermined acute angle on an inner surface of the hollow cylindrical piece. Inserting step; manufacturing method of the tapered piston pin further comprising. The method of claim 6, And said second predetermined acute angle of said second taper is less than said first predetermined acute angle of said first taper. The method of claim 6, And said second predetermined acute angle of said second taper is greater than said first predetermined acute angle of said first taper. In the method of manufacturing the tapered piston pin, Perforating the slug piece to form a slug piece in the hollow cylindrical piece; And And die extruding the hollow cylindrical piece at both ends to form the hollow cylindrical piece having a tapered length at both ends of the inner surface of the hollow cylindrical piece. The method of claim 9, Inserting a first die punch into an end of the hollow cylindrical piece, And the first die punch forms a first taper on an inner surface of the cylindrical piece at a first acute angle. The method of claim 10, Inserting a second die punch into the end of the hollow cylindrical piece, And said second die punch forms a second taper at a second predetermined acute angle on an inner surface of said hollow cylindrical piece. The method of claim 11, And said second predetermined acute angle of said second taper is less than said first predetermined acute angle of said first taper. The method of claim 11, And said second predetermined acute angle of said second taper is greater than said first predetermined acute angle of said first taper. Cutting the metal rod into substantially cylindrical slug pieces; Die extruding the slug piece to form a first cavity in the slug piece; Die extruding the slug piece to form a second cavity in the slug piece; Drilling the slug piece so as to form the slug piece in the hollow cylindrical piece; And And die-extruding the hollow cylindrical piece at both ends to form the hollow cylindrical piece having a tapered length at both ends of the inner surface of the hollow cylindrical piece. The method of claim 14, Manufactured using the step of inserting a first die punch into an end of the hollow cylindrical piece, And the first die punch forms a first taper on an inner surface of the cylindrical piece at a first acute angle. The method of claim 15, And inserting a second die punch into the end of the hollow cylindrical piece, And the second die punch forms a second taper at a second predetermined acute angle on an inner surface of the hollow cylindrical piece. The method of claim 16, And the second predetermined acute angle of the second taper is less than the first predetermined acute angle of the first taper. The method of claim 16, And the second predetermined acute angle of the second taper is greater than the first predetermined acute angle of the first taper.

Images